tools/nolibc: add timerfd functionality

This is used in various selftests and will be handy when integrating
those with nolibc.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20250428-nolibc-misc-v2-10-3c043eeab06c@linutronix.de
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

tools/include/nolibc/Makefile

@@ -53,6 +53,7 @@ all_files := \
 		sys/stat.h \
 		sys/syscall.h \
 		sys/time.h \
+		sys/timerfd.h \
 		sys/types.h \
 		sys/wait.h \
 		time.h \

tools/include/nolibc/nolibc.h

@@ -102,6 +102,7 @@
 #include "sys/stat.h"
 #include "sys/syscall.h"
 #include "sys/time.h"
+#include "sys/timerfd.h"
 #include "sys/wait.h"
 #include "ctype.h"
 #include "elf.h"

tools/include/nolibc/sys/timerfd.h

@@ -0,0 +1,87 @@
+/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
+/*
+ * timerfd definitions for NOLIBC
+ * Copyright (C) 2025 Thomas Weißschuh <thomas.weissschuh@linutronix.de>
+ */
+
+/* make sure to include all global symbols */
+#include "../nolibc.h"
+
+#ifndef _NOLIBC_SYS_TIMERFD_H
+#define _NOLIBC_SYS_TIMERFD_H
+
+#include "../sys.h"
+#include "../time.h"
+
+#include <linux/timerfd.h>
+
+
+static __attribute__((unused))
+int sys_timerfd_create(int clockid, int flags)
+{
+	return my_syscall2(__NR_timerfd_create, clockid, flags);
+}
+
+static __attribute__((unused))
+int timerfd_create(int clockid, int flags)
+{
+	return __sysret(sys_timerfd_create(clockid, flags));
+}
+
+
+static __attribute__((unused))
+int sys_timerfd_gettime(int fd, struct itimerspec *curr_value)
+{
+#if defined(__NR_timerfd_gettime)
+	return my_syscall2(__NR_timerfd_gettime, fd, curr_value);
+#elif defined(__NR_timerfd_gettime64)
+	struct __kernel_itimerspec kcurr_value;
+	int ret;
+
+	ret = my_syscall2(__NR_timerfd_gettime64, fd, &kcurr_value);
+	__nolibc_timespec_kernel_to_user(&kcurr_value.it_interval, &curr_value->it_interval);
+	__nolibc_timespec_kernel_to_user(&kcurr_value.it_value, &curr_value->it_value);
+	return ret;
+#else
+	return __nolibc_enosys(__func__, fd, curr_value);
+#endif
+}
+
+static __attribute__((unused))
+int timerfd_gettime(int fd, struct itimerspec *curr_value)
+{
+	return __sysret(sys_timerfd_gettime(fd, curr_value));
+}
+
+
+static __attribute__((unused))
+int sys_timerfd_settime(int fd, int flags,
+			const struct itimerspec *new_value, struct itimerspec *old_value)
+{
+#if defined(__NR_timerfd_settime)
+	return my_syscall4(__NR_timerfd_settime, fd, flags, new_value, old_value);
+#elif defined(__NR_timerfd_settime64)
+	struct __kernel_itimerspec knew_value, kold_value;
+	int ret;
+
+	__nolibc_timespec_user_to_kernel(&new_value->it_value, &knew_value.it_value);
+	__nolibc_timespec_user_to_kernel(&new_value->it_interval, &knew_value.it_interval);
+	ret = my_syscall4(__NR_timerfd_settime64, fd, flags, &knew_value, &kold_value);
+	if (old_value) {
+		__nolibc_timespec_kernel_to_user(&kold_value.it_interval, &old_value->it_interval);
+		__nolibc_timespec_kernel_to_user(&kold_value.it_value, &old_value->it_value);
+	}
+	return ret;
+#else
+	return __nolibc_enosys(__func__, fd, flags, new_value, old_value);
+#endif
+}
+
+static __attribute__((unused))
+int timerfd_settime(int fd, int flags,
+		    const struct itimerspec *new_value, struct itimerspec *old_value)
+{
+	return __sysret(sys_timerfd_settime(fd, flags, new_value, old_value));
+}
+
+#endif /* _NOLIBC_SYS_TIMERFD_H */